1. Field of the Invention
The present invention is related to measuring the distance between two objects based on a time of flight of a probe signal sent between the objects. In particular, the present invention is related to measuring the distance between two objects using a positioning system, such as the Global Positioning System (GPS).
2. Discussion of the Related Art
The “time of flight” of a signal is often used to determine the position or the time of the objects. The “time of flight” is a time-offset measured between the time a probe signal is sent and the time the probe signal is received. The distance between the objects is the product of the time of flight and the propagation speed of the probe signal (e.g., the speed of light, in the case of a GPS signal). In the GPS system, the time of flight is referred to as a “pseudo-range measurement.” In many systems, the time of flight may be used in additional calculations. For example, in the GPS system, multiple pseudo-range measurements are used to determine a 3-dimensional position of an object relative to the earth. The clock offset may also be calculated to further refine the accuracy in the calculated location. Detailed descriptions of various aspects of the GPS system may be found, for example, in “Global Position System: Signals, Measurement and Performance” (“Enge”) by Pratap Misra and Per Enge, and its cited references.